Seasonal and Inter-Annual Controls on CO2 Flux in Arctic Alaska

The Arctic landscape holds massive potential to affect the global carbon balance. Soils of the northern permafrost region account for approximately 50 percent of the estimated global below-ground organic carbon pool. The total soil organic carbon in the first 3 m in northern circumpolar permafrost, excluding yedoma, is ca.1024 PgC. Under a projected warmer and drier climate, the decomposition and release of even a fraction of these massive quantities of soil carbon in Arctic soils could create an additional positive feedback and further warming of the planet.

It is critical to continually assess the rate of carbon flux from the Arctic landscape, and study how the thawing and rising ground temperature over the region affect the atmospheric concentrations of CO2 and CH4. Long-term measurements are especially critical as Arctic terrestrial ecosystems are changing dramatically in response to persistent and accelerating regional warming trends. Dramatic changes in Arctic hydrology have become evident in recent years. Changes in hydrology including soil water content, lake formation, and lake loss have profound effects on CO2 and CH4 fluxes.

Global Change Research Group (GCRG) at San Diego State University (SDSU) has maintained eddy covariance flux towers at three sites in Arctic Alaska: Barrow, Atqasuk, and Ivotuk. The three sites form a 300 km N-S transect on the North Slope of Alaska, each site representing distinct vegetation communities common to the Arctic. Prior flux measurements at the three SDSU-GCRG flux tower sites have generated important discoveries about the role of the Arctic regions to global climate change. Data from SDSU-GCRG flux towers in the Arctic support high-impact research by scientists at SDSU and a wide array of research institution, as evidenced by journal publications.

The importance of these tower measurements cannot be understated: these towers create a long-term record of one of the largest, most volatile carbon stocks on the planet. These towers measure net fluxes of CO2, CH4, H2O vapor, sensible heat, latent heat, and momentum in addition to standard meteorological and environmental variables (MET data), and all data are made available in the public domain through direct access via selected online databases, including the Carbon Dioxide Information Analysis Center website, the AmeriFlux website, the GCRG website, and others.

Data collected by the project are being used to determine the seasonal and inter-annual patterns of CO2 and methane flux, and their relationship to changes in environmental factors. The data are also being used to identify important differences in carbon flux at different Arctic landscape types. Project results have the potential to contribute to the refinement global carbon flux models. The information on spatial, annual, and inter-annual variation in sensible and latent heat flux and CO2 and CH4 fluxes is critical to better inform ecosystem and land surface models and to improve and make more realistic their operation under current and likely future conditions.